1. Field of the Invention
This invention relates to the process of writing to memory. More specifically, this invention relates to the process of writing data into memory using low-voltage-swing signals on global bit-lines.
2. Related Art
Rapid advances in computing technology have made it possible to perform trillions of computational operations each second on data sets that are sometimes as large as a trillion bytes. These advances can be largely attributed to the exponential increase in the size and complexity of integrated circuits.
Unfortunately, in conjunction with the increase in size and complexity, the power consumption of integrated circuits has also increased. As a result, there is a strong need for integrated circuits that consume less power without sacrificing functionality.
Almost every electronic device contains some form of memory. In many scenarios, the power consumption of a memory can limit its applicability to the electronic device. For example, a memory's power consumption can become a limiting factor due to the system's inadequate heat dissipation capabilities. Similarly, due to the scarcity of battery power in a mobile device, a memory's power consumption can become a limiting factor.
Hence, it is very important to find ways to reduce the power consumption of memories within computer systems.
Memory chips are typically organized hierarchically, with individual memory cells grouped together to share data lines. These data lines are called “local bit-lines,” and are usually paired as true and complement wires. The cells that are coupled with these local bit-lines are then grouped together to form larger sets such that these larger sets share another pair of true and complement data lines.
This hierarchy of data lines can extend for one or more levels. The data lines at the top of this hierarchy are called “global bit-lines.”
During a read operation, individual memory cells drive the local bit-lines, which in turn drive the higher levels of data lines, eventually driving the global bit-lines. During a write operation, the reverse happens: data is driven onto the global bit-lines and from there it appears on successively lower data lines, eventually appearing on the local bit-lines and writing into the memory cells.
Global bit-lines typically use a high-voltage-swing signal for stable (reliable) writes to memory cells and have high capacitances because they span the entire memory array. Moreover, global bit-lines are active on every memory operation. As a result, during writes, global bit-lines can end up using a significant fraction of the memory's power consumption.
Hence, what is needed is a method and apparatus that consumes less power while writing to a memory.